Fibroblast growth factor-2 levels are elevated in the cerebrospinal fluid of multiple sclerosis patients

Potential therapeutic and diagnostic approaches of exosomes in multiple sclerosis pathophysiology

Exosomes are bilayer lipid vesicles that are released by cells and contain proteins, nucleic acids, and lipids. They can be internalized by other cells, inducing inflammatory responses and instigating toxicities in the recipient cells. Exosomes can also serve as therapeutic vehicles by transporting protective cargo to maintain homeostasis. Multiple studies have shown that exosomes can initiate and participate in the regulation of neuroinflammation, improve neurogenesis, and are closely related to the pathogenesis of central nervous system (CNS) diseases, including multiple sclerosis (MS). Exosomes can be secreted by both neurons and glial cells in the CNS, and their contents change with disease occurrence. Due to their ability to penetrate the blood-brain barrier and their stability in peripheral fluids, exosomes are attractive biomarkers of CNS diseases. In recent years, exosomes have emerged as potential therapeutic agents for CNS diseases, including MS. However, the molecular pathways in the pathogenesis of MS are still unknown, and further research is needed to fully understand the role of exosomes in the occurrence or improvement of MS disease. Thereby, in this review, we intend to provide a more complete understanding of the pathways in which exosomes are involved and affect the occurrence or improvement of MS disease.

Exosomes in the Diagnosis of Neuropsychiatric Diseases: A Review

Exosomes are 30-150 nm small extracellular vesicles (sEVs) which are highly stable and encapsulated by a phospholipid bilayer. Exosomes contain proteins, lipids, RNAs (mRNAs, microRNAs/miRNAs, long non-coding RNAs/lncRNAs), and DNA of their parent cell. In pathological conditions, the composition of exosomes is altered, making exosomes a potential source of biomarkers for disease diagnosis. Exosomes can cross the blood-brain barrier (BBB), which is an advantage for using exosomes in the diagnosis of central nervous system (CNS) diseases. Neuropsychiatric diseases belong to the CNS diseases, and many potential diagnostic markers have been identified for neuropsychiatric diseases. Here, we review the potential diagnostic markers of exosomes in neuropsychiatric diseases and discuss the potential application of exosomal biomarkers in the early and accurate diagnosis of these diseases. Additionally, we outline the limitations and future directions of exosomes in the diagnosis of neuropsychiatric diseases.

Exosome Content-Mediated Signaling Pathways in Multiple Sclerosis

Exosomes are small extracellular vesicles with a complex lipid-bilayer surface and 30-150 nm diameter. These vesicles play a critical role in intercellular signaling networks during physiopathological processes through data trafficking and cell reprogramming. It has been demonstrated that exosomes are involved in a variety of central nervous system (CNS) disorders such as multiple sclerosis (MS). Exosome mediators' cell-to-cell communication is possibly by delivering their contents such as proteins, RNAs (coding and non-coding), DNAs (mitochondrial and genomic), and transposable elements to the target cells. Exosomal microRNAs (miRNAs) differ in their expression patterns in MS disease, thereby providing novel diagnostic and prognostic biomarkers and therapeutic options for better treatment of MS disease. Furthermore, these microvesicles are non-immunogenic and non-toxic therapeutic tools for transferring miRNAs across the blood-brain barrier (BBB). Collectively, exosomes could be used as novel drug delivery devices for the treatment of MS patients. This review summarized research regarding the exosomes from serum, plasma, PBMC, and other cells in MS patients and experimental models. We also provide a critical view of exosome content-mediated signaling pathways in MS, including TNF-α, TGF-β, NF-κB, and Wnt pathways. The use of exosomes as a therapeutic potential in MS has also been discussed.

The small molecule fibroblast growth factor receptor inhibitor infigratinib exerts anti-inflammatory effects and remyelination in a model of multiple sclerosis

BACKGROUND AND PURPOSE

Fibroblast growth factors and receptors (FGFR) have been shown to modulate inflammation and neurodegeneration in multiple sclerosis (MS). The selective FGFR inhibitor infigratinib has been shown to be effective in cancer models. Here, we investigate the effects of infigratinib on prevention and suppression of first clinical episodes of myelin oligodendrocyte glycoprotein (MOG)35-55 -induced experimental autoimmune encephalomyelitis (EAE) in mice.

EXPERIMENTAL APPROACH

The FGFR inhibitor infigratinib was given over 10 days from the time of experimental autoimmune encephalomyelitis induction or the onset of symptoms. The effects of infigratinib on proliferation, cytotoxicity and FGFR signalling proteins were studied in lymphocyte cell lines and microglial cells.

KEY RESULTS

Administration of infigratinib prevented by 40% and inhibited by 65% first clinical episodes of the induced experimental autoimmune encephalomyelitis. In the spinal cord, infiltration of lymphocytes and macrophages/microglia, destruction of myelin and axons were reduced by infigratinib. Infigratinib enhanced the maturation of oligodendrocytes and increased remyelination. In addition, infigratinib resulted in an increase of myelin proteins and a decrease in remyelination inhibitors. Further, lipids associated with neurodegeneration such as lysophosphatidylcholine and ceramide were decreased as were proliferation of T cells and microglial cells.

CONCLUSION AND IMPLICATIONS

This proof of concept study demonstrates the therapeutic potential of targeting FGFRs in a disease model of multiple sclerosis. Application of oral infigratinib resulted in anti-inflammatory and remyelinating effects. Thus, infigratinib may have the potential to slow disease progression or even to improve the disabling symptoms of multiple sclerosis.

Multiplex Analysis of Cerebrospinal Fluid and Serum Exosomes MicroRNAs of Untreated Relapsing Remitting Multiple Sclerosis (RRMS) and Proposing Noninvasive Diagnostic Biomarkers

Exosomal microRNAs (miRNAs) are emerging diagnostic biomarkers for neurodegenerative diseases. In this study, we aimed to detect relapsing-remitting multiple sclerosis (RRMS)-specific miRNAs in cerebrospinal fluid (CSF) and serum exosomes with diagnostic potential. One ml of CSF and serum sample were collected from each of the 30 untreated RRMS patients and healthy controls (HCs). A panel of 18 miRNAs affecting inflammatory responses was applied, and qRT-PCR was conducted to detect differentially expressed exosomal miRNAs in CSF and serum of RRMS patients. We identified that 17 out of 18 miRNAs displayed different patterns in RRMS patients compared to HCs. Let-7 g-5p, miR-18a-5p, miR-145-5p, and miR-374a-5p with dual pro-inflammatory and anti-inflammatory actions and miR-150-5p and miR-342-3p with anti-inflammatory action were significantly upregulated in both CSF and serum-derived exosomes of RRMS patients compared to corresponding HCs. Additionally, anti-inflammatory miR-132-5p and pro-inflammatory miR-320a-5p were significantly downregulated in both CSF and serum-derived exosomes of RRMS patients compared to HCs. Ten of 18 miRNAs were differentially expressed in CSF and serum exosomes of the patients. Furthermore, miR-15a-5p, miR-19b-3p, and miR-432-5p were upregulated, and miR-17-5p was downregulated only in CSF exosomes. Interestingly, U6 housekeeping gene was differentially expressed in CSF and serum exosomes, in both RRMS and HCs. As the first report describing CSF exosomal miRNAs expression profile compared to that of serum exosomes in untreated RRMS patients, we showed that CSF and serum exosomes are not identical in terms of biological compounds and display different patterns in miRNAs and U6 expression.

FGF/FGFR system in the central nervous system demyelinating disease: Recent progress and implications for multiple sclerosis

BACKGROUND

With millions of victims worldwide, multiple sclerosis is the second most common cause of disability among young adults. Although formidable advancements have been made in understanding the disease, the neurodegeneration associated with multiple sclerosis is only partially counteracted by current treatments, and effective therapy for progressive multiple sclerosis remains an unmet need. Therefore, new approaches are required to delay demyelination and the resulting disability and to restore neural function by promoting remyelination and neuronal repair.

AIMS

The article reviews the latest literature in this field.

MATERIALS AND METHODS

The fibroblast growth factor (FGF) signaling pathway is a promising target in progressive multiple sclerosis.

DISCUSSION

FGF signal transduction contributes to establishing the oligodendrocyte lineage, neural stem cell proliferation and differentiation, and myelination of the central nervous system. Furthermore, FGF signaling is implicated in the control of neuroinflammation. In recent years, interventions targeting FGF, and its receptor (FGFR) have been shown to ameliorate autoimmune encephalomyelitis symptoms in multiple sclerosis animal models moderately.

CONCLUSION

Here, we summarize the recent findings and investigate the role of FGF/FGFR signaling in the onset and progression, discuss the potential therapeutic advances, and offer fresh insights into managing multiple sclerosis.

Interferon Beta-1a versus Combined Interferon Beta-1a and Oligodendrocyte-Specific FGFR1 Deletion in Experimental Autoimmune Encephalomyelitis

Recombinant beta interferons-1 (IFNβ-1) are used as first line therapies in patients with relapsing multiple sclerosis (MS), a chronic inflammatory and neurodegenerative disease of the CNS. IFNβ-1a/b has moderate effects on the prevention of relapses and slowing of disease progression. Fibroblast growth factors (FGFs) and FGF receptors (FGFRs) are known to play a key role in the pathology of MS and its model EAE. To investigate the effects of short-term treatment with s.c. IFNβ-1a versus the combined application of s.c. IFNβ-1a and oligodendrocyte-specific deletion of FGFR1 (Fgfr1^ind−/− mice) in MOG_35-55-induced EAE. IFNβ-1a (30 mg/kg) was applied s.c. from days 0–7 p.i. of EAE in controls and Fgfr1^ind−/− mice. FGFR signaling proteins associated with inflammation/degeneration in MS/EAE were analyzed by western blot in the spinal cord. Further, FGFR1 in Oli-neu oligodendrocytes were inhibited by PD166866 and treated with IFNβ-1a (400 ng/mL). Application of IFNβ-1a over 8 days resulted in less symptoms only at the peak of disease (days 9–11) compared to controls. Application of IFNβ-1a in Fgfr1^ind−/− mice resulted in less symptoms primarily in the chronic phase of EAE. Fgfr1^ind−/− mice treated with IFNβ-1a showed increased expression of pERK and BDNF. In Oli-neu oligodendrocytes, treatment with PD166866 and IFNβ-1a also showed an increased expression of pERK and BDNF/TrkB. These data suggest that the beneficial effects in the chronic phase of EAE and on signaling molecules associated with ERK and BDNF expression are caused by the modulation of FGFR1 and not by interferon beta-1a. FGFR may be a potential target for therapy in MS.

Molecular Mechanisms of Immunosenescene and Inflammaging: Relevance to the Immunopathogenesis and Treatment of Multiple Sclerosis

Aging is characterized, amongst other features, by a complex process of cellular senescence involving both innate and adaptive immunity, called immunosenescence and associated to inflammaging, a low-grade chronic inflammation. Both processes fuel each other and partially explain increasing incidence of cancers, infections, age-related autoimmunity, and vascular disease as well as a reduced response to vaccination. Multiple sclerosis (MS) is a lifelong disease, for which considerable progress in disease-modifying therapies (DMTs) and management has improved long-term survival. However, disability progression, increasing with age and disease duration, remains. Neurologists are now involved in caring for elderly MS patients, with increasing comorbidities. Aging of the immune system therefore has relevant implications for MS pathogenesis, response to DMTs and the risks mediated by these treatments. We propose to review current evidence regarding markers and molecular mechanisms of immunosenescence and their relevance to understanding MS pathogenesis. We will focus on age-related changes in the innate and adaptive immune system in MS and other auto-immune diseases, such as systemic lupus erythematosus and rheumatoid arthritis. The consequences of these immune changes on MS pathology, in interaction with the intrinsic aging process of central nervous system resident cells will be discussed. Finally, the impact of immunosenescence on disease evolution and on the safety and efficacy of current DMTs will be presented.

New Epidermal-Growth-Factor-Related Insights Into the Pathogenesis of Multiple Sclerosis: Is It Also Epistemology?

Recent findings showing that epidermal growth factor (EGF) is significantly decreased in the cerebrospinal fluid (CSF) and spinal cord (SC) of living or deceased multiple sclerosis (MS) patients, and that its repeated administration to rodents with chemically- or virally-induced demyelination of the central nervous system (CNS) or experimental allergic encephalomyelitis (EAE) prevents demyelination and inflammatory reactions in the CNS, have led to a critical reassessment of the MS pathogenesis, partly because EGF is considered to have little or no role in immunology. EGF is the only myelinotrophic factor that has been tested in the CSF and spinal cord of MS patients, and it has been shown there is a good correspondence between liquid and tissue levels. This review: (a) briefly summarises the positive EGF effects on neural stem cells, oligodendrocyte cell lineage, and astrocytes in order to explain, at least in part, the biological basis of the myelin loss and remyelination failure in MS; and (b) after a short analysis of the evolution of the principle of cause-effect in the history of Western philosophy, highlights the lack of any experimental immune-, toxin-, or virus-mediated model that precisely reproduces the histopathological features and “clinical” symptoms of MS, thus underlining the inapplicability of Claude Bernard's crucial sequence of “observation, hypothesis, and hypothesis testing.” This is followed by a discussion of most of the putative non-immunologically-linked points of MS pathogenesis (abnormalities in myelinotrophic factor CSF levels, oligodendrocytes (ODCs), astrocytes, extracellular matrix, and epigenetics) on the basis of Popper's falsification principle, and the suggestion that autoimmunity and phologosis reactions (surely the most devasting consequences of the disease) are probably the last links in a chain of events that trigger the reactions. As it is likely that there is a lack of other myelinotrophic growth factors because myelinogenesis is controlled by various CNS and extra-CNS growth factors and other molecules within and outside ODCs, further studies are needed to investigate the role of non-immunological molecules at the time of the onset of the disease. In the words of Galilei, the human mind should be prepared to understand what nature has created.

New insights into the role of fibroblast growth factors in Alzheimer's disease

Alzheimer's disease (AD), acknowledged as the most common progressive neurodegenerative disorder, is the leading cause of dementia in the elderly. The characteristic pathologic hallmarks of AD-including the deposition of extracellular senile plaques (SP) formation, intracellular neurofibrillary tangles, and synaptic loss, along with prominent vascular dysfunction and cognitive impairment-have been observed in patients. Fibroblast growth factors (FGFs), originally characterized as angiogenic factors, are a large family of signaling molecules that are implicated in a wide range of biological functions in brain development, maintenance and repair, as well as in the pathogenesis of brain-related disorders including AD. Many studies have focused on the implication of FGFs in AD pathophysiology. In this review, we will provide a summary of recent findings regarding the role of FGFs and their receptors in the pathogenesis of AD, and discuss the possible opportunities for targeting these molecules as novel treatment strategies in AD.

Oligodendrocyte-Specific Deletion of FGFR1 Reduces Cerebellar Inflammation and Neurodegeneration in MOG35-55-Induced EAE

Multiple sclerosis (MS) is a chronic inflammatory and degenerative disease of the central nervous system (CNS). MS commonly affects the cerebellum causing acute and chronic symptoms. Cerebellar signs significantly contribute to clinical disability, and symptoms such as tremor, ataxia, and dysarthria are difficult to treat. Fibroblast growth factors (FGFs) and their receptors (FGFRs) are involved in demyelinating pathologies such as MS. In autopsy tissue from patients with MS, increased expression of FGF1, FGF2, FGF9, and FGFR1 was found in lesion areas. Recent research using mouse models has focused on regions such as the spinal cord, and data on the expression of FGF/FGFR in the cerebellum are not available. In recent EAE studies, we detected that oligodendrocyte-specific deletion of FGFRs results in a milder disease course, less cellular infiltrates, and reduced neurodegeneration in the spinal cord. The objective of this study was to characterize the role of FGFR1 in oligodendrocytes in the cerebellum. Conditional deletion of FGFR1 in oligodendrocytes (Fgfr1^ind−/−) was achieved by tamoxifen application, EAE was induced using the MOG_35-55 peptide. The cerebellum was analyzed by histology, immunohistochemistry, and western blot. At day 62 p.i., Fgfr1^ind−/− mice showed less myelin and axonal degeneration compared to FGFR1-competent mice. Infiltration of CD3(+) T cells, Mac3(+) cells, B220(+) B cells and IgG(+) plasma cells in cerebellar white matter lesions (WML) was less in Fgfr1^ind−/−mice. There were no effects on the number of OPC or mature oligodendrocytes in white matter lesion (WML). Expression of FGF2 and FGF9 associated with less myelin and axonal degeneration, and of the pro-inflammatory cytokines IL-1β, IL-6, and CD200 was downregulated in Fgfr1^ind−/− mice. The FGF/FGFR signaling protein pAkt, BDNF, and TrkB were increased in Fgfr1^ind−/− mice. These data suggest that cell-specific deletion of FGFR1 in oligodendrocytes has anti-inflammatory and neuroprotective effects in the cerebellum in the EAE disease model of MS.

Effects of FGFR Tyrosine Kinase Inhibition in OLN-93 Oligodendrocytes

Fibroblast growth factor (FGF) signaling is involved in the pathogenesis of multiple sclerosis (MS). Data from neuropathology studies suggest that FGF signaling contributes to the failure of remyelination in MS. In MOG_35–55-induced EAE, oligodendrocyte-specific deletion of FGFR1 and FGFR2 resulted in a less severe disease course, reduced inflammation, myelin and axon degeneration and changed FGF/FGFR and BDNF/TrkB signaling. Since signaling cascades in oligodendrocytes could not be investigated in the EAE studies, we here aimed to characterize FGFR-dependent oligodendrocyte-specific signaling in vitro. FGFR inhibition was achieved by application of the multi-kinase-inhibitor dovitinib and the FGFR1/2/3-inhibitor AZD4547. Both substances are potent inhibitors of FGF signaling; they are effective in experimental tumor models and patients with malignancies. Effects of FGFR inhibition in oligodendrocytes were studied by immunofluorescence microscopy, protein and gene analyses. Application of the tyrosine kinase inhibitors reduced FGFR1, phosphorylated ERK and Akt expression, and it enhanced BDNF and TrkB expression. Furthermore, the myelin proteins CNPase and PLP were upregulated by FGFR inhibition. In summary, inhibition of FGFR signaling in oligodendrocytes can be achieved by application of tyrosine kinase inhibitors. Decreased phosphorylation of ERK and Akt is associated with an upregulation of BDNF/TrkB signaling, which may be responsible for the increased production of myelin proteins. Furthermore, these data suggest that application of FGFR inhibitors may have the potential to promote remyelination in the CNS.

Fibroblast Growth Factor Signalling in the Diseased Nervous System

Fibroblast growth factors (FGFs) act as key signalling molecules in brain development, maintenance, and repair. They influence the intricate relationship between myelinating cells and axons as well as the association of astrocytic and microglial processes with neuronal perikarya and synapses. Advances in molecular genetics and imaging techniques have allowed novel insights into FGF signalling in recent years. Conditional mouse mutants have revealed the functional significance of neuronal and glial FGF receptors, not only in tissue protection, axon regeneration, and glial proliferation but also in instant behavioural changes. This review provides a summary of recent findings regarding the role of FGFs and their receptors in the nervous system and in the pathogenesis of major neurological and psychiatric disorders.

FGF/FGFR Pathways in Multiple Sclerosis and in Its Disease Models

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disease of the central nervous system (CNS) affecting more than two million people worldwide. In MS, oligodendrocytes and myelin sheaths are destroyed by autoimmune-mediated inflammation, while remyelination is impaired. Recent investigations of post-mortem tissue suggest that Fibroblast growth factor (FGF) signaling may regulate inflammation and myelination in MS. FGF2 expression seems to correlate positively with macrophages/microglia and negatively with myelination; FGF1 was suggested to promote remyelination. In myelin oligodendrocyte glycoprotein (MOG)35-55-induced experimental autoimmune encephalomyelitis (EAE), systemic deletion of FGF2 suggested that FGF2 may promote remyelination. Specific deletion of FGF receptors (FGFRs) in oligodendrocytes in this EAE model resulted in a decrease of lymphocyte and macrophage/microglia infiltration as well as myelin and axon degeneration. These effects were mediated by ERK/Akt phosphorylation, a brain-derived neurotrophic factor, and downregulation of inhibitors of remyelination. In the first part of this review, the most important pharmacotherapeutic principles for MS will be illustrated, and then we will review recent advances made on FGF signaling in MS. Thus, we will suggest application of FGFR inhibitors, which are currently used in Phase II and III cancer trials, as a therapeutic option to reduce inflammation and induce remyelination in EAE and eventually MS.

Oligodendrocyte-specific deletion of FGFR2 ameliorates MOG35-55 -induced EAE through ERK and Akt signalling

Fibroblast growth factors (FGFs) and their receptors (FGFRs) are involved in demyelinating pathologies including multiple sclerosis (MS). In our recent study, oligodendrocyte‐specific deletion of FGFR1 resulted in a milder disease course, less inflammation, reduced myelin and axon damage in EAE. The objective of this study was to elucidate the role of oligodendroglial FGFR2 in MOG_35‐55‐induced EAE. Oligodendrocyte‐specific knockout of FGFR2 (Fgfr2^ind−/−) was achieved by application of tamoxifen; EAE was induced using the MOG_35‐55 peptide. EAE symptoms were monitored over 62 days. Spinal cord tissue was analysed by histology, immunohistochemistry and western blot. Fgfr2^ind−/− mice revealed a milder disease course, less myelin damage and enhanced axonal density. The number of oligodendrocytes was not affected in demyelinated areas. However, protein expression of FGFR2, FGF2 and FGF9 was downregulated in Fgfr2^ind−/− mice. FGF/FGFR dependent signalling proteins were differentially regulated; pAkt was upregulated and pERK was downregulated in Fgfr2^ind−/− mice. The number of CD3(+) T cells, Mac3(+) cells and B220(+) B cells was less in demyelinated lesions of Fgfr2^ind−/− mice. Furthermore, expression of IL‐1β, TNF‐α and CD200 was less in Fgfr2^ind−/− mice than controls. Fgfr2^ind−/− mice showed an upregulation of PLP and downregulation of the remyelination inhibitors SEMA3A and TGF‐β expression. These data suggest that cell‐specific deletion of FGFR2 in oligodendrocytes has anti‐inflammatory and neuroprotective effects accompanied by changes in FGF/FGFR dependent signalling, inflammatory cytokines and expression of remyelination inhibitors. Thus, FGFRs in oligodendrocytes may represent potential targets for the treatment of inflammatory and demyelinating diseases including MS.

What Can We Learn from FGF-2 Isoform-Specific Mouse Mutants? Differential Insights into FGF-2 Physiology In Vivo

Fibroblast growth factor 2 (FGF-2), ubiquitously expressed in humans and mice, is functionally involved in cell growth, migration and maturation in vitro and in vivo. Based on the same mRNA, an 18-kilo Dalton (kDa) FGF-2 isoform named FGF-2 low molecular weight (FGF-2LMW) isoform is translated in humans and rodents. Additionally, two larger isoforms weighing 21 and 22 kDa also exist, summarized as the FGF-2 high molecular weight (FGF-2HMW) isoform. Meanwhile, the human FGF-2HMW comprises a 22, 23, 24 and 34 kDa protein. Independent studies verified a specific intracellular localization, mode of action and tissue-specific spatiotemporal expression of the FGF-2 isoforms, increasing the complexity of their physiological and pathophysiological roles. In order to analyze their spectrum of effects, FGF-2LMW knock out (ko) and FGF-2HMWko mice have been generated, as well as mice specifically overexpressing either FGF-2LMW or FGF-2HMW. So far, the development and functionality of the cardiovascular system, bone formation and regeneration as well as their impact on the central nervous system including disease models of neurodegeneration, have been examined. This review provides a summary of the studies characterizing the in vivo effects modulated by the FGF-2 isoforms and, thus, offers a comprehensive overview of its actions in the aforementioned organ systems.

Protective Functions of Reactive Astrocytes Following Central Nervous System Insult

Astrocytes play important roles in numerous central nervous system disorders including autoimmune inflammatory, hypoxic, and degenerative diseases such as Multiple Sclerosis, ischemic stroke, and Alzheimer’s disease. Depending on the spatial and temporal context, activated astrocytes may contribute to the pathogenesis, progression, and recovery of disease. Recent progress in the dissection of transcriptional responses to varying forms of central nervous system insult has shed light on the mechanisms that govern the complexity of reactive astrocyte functions. While a large body of research focuses on the pathogenic effects of reactive astrocytes, little is known about how they limit inflammation and contribute to tissue regeneration. However, these protective astrocyte pathways might be of relevance for the understanding of the underlying pathology in disease and may lead to novel targeted approaches to treat autoimmune inflammatory and degenerative disorders of the central nervous system. In this review article, we have revisited the emerging concept of protective astrocyte functions and discuss their role in the recovery from inflammatory and ischemic disease as well as their role in degenerative disorders. Focusing on soluble astrocyte derived mediators, we aggregate the existing knowledge on astrocyte functions in the maintenance of homeostasis as well as their reparative and tissue-protective function after acute lesions and in neurodegenerative disorders. Finally, we give an outlook of how these mediators may guide future therapeutic strategies to tackle yet untreatable disorders of the central nervous system.

Immune and central nervous system-related miRNAs expression profiling in monocytes of multiple sclerosis patients

It is widely recognized that monocytes-macrophages adopt a wide variety of phenotypes, influencing the inflammatory activity and demyelination in Multiple Sclerosis (MS). However, how the phenotype of human monocytes evolves in the course of MS is largely unknown. The aim of our preliminary study was to analyse in monocytes of relapsing-remitting and progressive forms of MS patients the expression of a set of miRNAs which impact monocyte-macrophage immune function and their communication with brain cells. Quantitative PCR showed that miRNAs with anti-inflammatory functions, which promote pro-regenerative polarization, are increased in MS patients, while pro-inflammatory miR-155 is downregulated in the same patients. These changes may indicate the attempt of monocytes to counteract neuroinflammation. miR-124, an anti-inflammatory marker but also of myeloid cell quiescence was strongly downregulated, especially in progressive MS patients, suggesting complete loss of homeostatic monocyte function in the progressive disease phase. Profiling of miRNAs that control monocyte polarization may help to define not only the activation state of monocytes in the course of the disease but also novel pathogenic mechanisms.

Polarizing receptor activation dissociates fibroblast growth factor 2 mediated inhibition of myelination from its neuroprotective potential

Fibroblast growth factor (FGF) signaling contributes to failure of remyelination in multiple sclerosis, but targeting this therapeutically is complicated by its functional pleiotropy. We now identify FGF2 as a factor up-regulated by astrocytes in active inflammatory lesions that disrupts myelination via FGF receptor 2 (FGFR2) mediated activation of Wingless (Wnt) signaling; pharmacological inhibition of Wnt being sufficient to abrogate inhibition of myelination by FGF2 in tissue culture. Using a novel FGFR1-selective agonist (F2 V2) generated by deleting the N-terminal 26 amino acids of FGF2 we demonstrate polarizing signal transduction to favor FGFR1 abrogates FGF mediated inhibition of myelination but retains its ability to induce expression of pro-myelinating and immunomodulatory factors that include Cd93, Lif, Il11, Hbegf, Cxcl1 and Timp1. Our data provide new insights into the mechanistic basis of remyelination failure in MS and identify selective activation of FGFR1 as a novel strategy to induce a neuroprotective signaling environment in multiple sclerosis and other neurological diseases.

Combinatory Multifactor Treatment Effects on Primary Nanofiber Oligodendrocyte Cultures

Multiple sclerosis (MS) is a chronic inflammatory demyelinating and neurodegenerative disease of the central nervous system. Neurological deficits are attributed to inflammatory demyelination, which compromises axonal function and survival. These are mitigated in experimental models by rapid and often complete remyelination of affected axons, but in MS this endogenous repair mechanism frequently fails, leaving axons increasingly vulnerable to the detrimental effects of inflammatory and metabolic stress. Understanding the molecular basis of remyelination and remyelination failure is essential to develop improved therapies for this devastating disease. However, recent studies suggest that this is not due to a single dominant mechanism, but rather represents the biological outcome of multiple changes in the lesion microenvironment that combine to disrupt oligodendrocyte differentiation. This identifies a pressing need to develop technical platforms to investigate combinatory and/or synergistic effects of factors differentially expressed in MS lesions on oligodendrocyte proliferation and differentiation. Here we describe protocols using primary oligodendrocyte cultures from Bl6 mice on 384-well nanofiber plates to model changes affecting oligodendrogenesis and differentiation in the complex signaling environment associated with multiple sclerosis lesions. Using platelet-derived growth factor (PDGF–AA), fibroblast growth factor 2 (FGF2), bone morphogenetic protein 2 (BMP2) and bone morphogenetic protein 4 (BMP4) as representative targets, we demonstrate that we can assess their combinatory effects across a wide range of concentrations in a single experiment. This in vitro model is ideal for assessing the combinatory effects of changes in availability of multiple factors, thus more closely modelling the situation in vivo and furthering high-throughput screening possibilities.

Domperidone-induced elevation of serum prolactin levels and immune response in multiple sclerosis

Increasing systemic prolactin levels improves remyelination and neuronal survival in animal models of Multiple Sclerosis (MS), but it has been suggested that this therapeutic strategy may also increase inflammatory responses, and potentially harm patients. We analyzed serum prolactin and cytokine, chemokine and growth factor levels in sera from MS patients enrolled in two clinical trials who were treated with domperidone, a generic drug that increases systemic prolactin levels. In patients treated with domperidone, molecule levels changed little during follow up, while prolactin levels increased several-fold. We found no significant association between prolactin levels and radiological or clinical outcome.

Identification of candidate biomarkers in converting and non-converting clinically isolated syndrome by proteomics analysis of cerebrospinal fluid

Multiple sclerosis (MS) often starts in the form of clinically isolated syndrome (CIS) and only some of the CIS patients progress to relapsing-remitting MS (RRMS). Biomarkers to predict conversion from CIS to MS are thus greatly needed for making correct treatment decisions. To identify a predictive cerebrospinal fluid (CSF) protein, we analyzed the first-attack CSF samples of CIS patients who converted (CIS-MS) (n = 23) and did not convert (CIS-CIS) (n = 19) to RRMS in a follow-up period of 5 years using proteomics analysis by liquid chromatography tandem-mass spectrometry (LC-MS/MS) and verified by ELISA. Label-free differential proteomics analysis of CSF ensured that 637 proteins were identified and 132 of these proteins were found to be statistically significant. Further investigation with the ingenuity pathway analysis (IPA) software led to identification of three pathway networks mostly comprised proteins involved in inflammatory response, cellular growth and tissue proliferation. CSF levels of four of the most differentially expressed proteins belonging to the cellular proliferation network function, chitinase-3-like protein 1 (CHI3L1), tumor necrosis factor receptor superfamily member 21 (TNFRSF21), homeobox protein Hox-B3 (HOXB3) and iduronate 2-sulfatase (IDS), were measured by ELISA. CSF levels of HOXB3 were significantly increased in CIS-MS patients. Our results indicate that cell and tissue proliferation functions are dysregulated in MS as early as the first clinical episode. HOXB3 has emerged as a potential novel biomarker which might be used for prediction of CIS-MS conversion.

Exosome-associated miRNA profile as a prognostic tool for therapy response monitoring in multiple sclerosis patients

Multiple sclerosis (MS) is an autoimmune pathology leading to neurodegeneration. Because of the complexity and heterogenic etiology of this disease, diagnosis and treatment for individual patients are challenging. Exosome-associated microRNAs (miRNAs) have recently emerged as a new class of diagnostic biomarkers involved in both autoimmune and neurologic disorders. Interesting new evidence has emerged showing that circulating miRNAs are dysregulated in MS body fluids, including serum, plasma, and cerebrospinal fluid. We hypothesized that exosome-associated miRNAs could present a readily accessible blood-based assay for MS disease. We detected expression of miRNAs by quantitative PCR on a small cohort of MS patients. We analyzed circulating exosome-associated miRNAs of MS patients before and after therapy and found that 14 exosome-associated miRNAs were significantly down-regulated, while 2 exosome-associated miRNAs were significantly up-regulated in IFN-β-treated relapsing-remitting MS patients with response to therapy compared to those without response. We identified a serum miRNA panel that could be used to monitor the response to IFN-β therapy. Overall, these data suggest that circulating exosome-associated miRNA profiling could represent an easily detectable biomarker of disease and treatment response.-Manna, I., Iaccino, E., Dattilo, V., Barone, S., Vecchio, E., Mimmi, S., Filippelli, E., Demonte, G., Polidoro, S., Granata, A., Scannapieco, S., Quinto, I., Valentino, P., Quattrone, A. Exosome-associated miRNA profile as a prognostic tool for therapy response monitoring in multiple sclerosis patients.

Exosomal microRNA signatures in multiple sclerosis reflect disease status

Multiple Sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). There is currently no single definitive test for MS. Circulating exosomes represent promising candidate biomarkers for a host of human diseases. Exosomes contain RNA, DNA, and proteins, can cross the blood-brain barrier, and are secreted from almost all cell types including cells of the CNS. We hypothesized that serum exosomal miRNAs could present a useful blood-based assay for MS disease detection and monitoring. Exosome-associated microRNAs in serum samples from MS patients (n = 25) and matched healthy controls (n = 11) were profiled using small RNA next generation sequencing. We identified differentially expressed exosomal miRNAs in both relapsing-remitting MS (RRMS) (miR-15b-5p, miR-451a, miR-30b-5p, miR-342-3p) and progressive MS patient sera (miR-127-3p, miR-370-3p, miR-409-3p, miR-432-5p) in relation to controls. Critically, we identified a group of nine miRNAs (miR-15b-5p, miR-23a-3p, miR-223-3p, miR-374a-5p, miR-30b-5p, miR-433-3p, miR-485-3p, miR-342-3p, miR-432-5p) that distinguished relapsing-remitting from progressive disease. Eight out of nine miRNAs were validated in an independent group (n = 11) of progressive MS cases. This is the first demonstration that microRNAs associated with circulating exosomes are informative biomarkers not only for the diagnosis of MS, but in predicting disease subtype with a high degree of accuracy.

Oligodendroglial fibroblast growth factor receptor 1 gene targeting protects mice from experimental autoimmune encephalomyelitis through ERK/AKT phosphorylation

Fibroblast growth factors (FGFs) exert diverse biological effects by binding and activation of specific fibroblast growth factor receptors (FGFRs). FGFs and FGFRs have been implicated in demyelinating pathologies including multiple sclerosis. In vitro activation of the FGF2/FGFR1 pathway results in downregulation of myelin proteins. FGF1, 2 and 9 have been shown to be involved in the pathology of multiple sclerosis. Recent studies on the function of oligodendroglial FGFR1 in a model of toxic demyelination showed that deletion of FGFR1 led to increased remyelination and preservation of axonal density and an increased number of mature oligodendrocytes. In the present study the in vivo function of oligodendroglial FGFR1 was characterized using an oligodendrocyte-specific genetic approach in the most frequently used model of multiple sclerosis the MOG_35-55 -induced EAE. Oligodendroglial FGFR1 deficient mice (referred to as Fgfr1^ind-/- ) showed a significantly ameliorated disease course in MOG_35-55 -induced EAE. Less myelin and axonal loss, and reduced lymphocyte and macrophage/microglia infiltration were found in Fgfr1^ind-/- mice. The reduction in disease severity in Fgfr1^ind-/- mice was accompanied by ERK/AKT phosphorylation, and increased expression of BDNF and TrkB. Reduced proinflammatory cytokine and chemokine expression was seen in Fgfr1^ind-/- mice compared with control mice. Considering that FGFR inhibitors are used in cancer trials, the oligodendroglial FGFR1 pathway may provide a new target for therapy in multiple sclerosis.

The role of growth factors as a therapeutic approach to demyelinating disease

A variety of growth factors are being explored as therapeutic agents relevant to the axonal and oligodendroglial deficits that occur as a result of demyelinating lesions such as are evident in Multiple Sclerosis (MS). This review focuses on five such proteins that are present in the lesion site and impact oligodendrocyte regeneration. It then presents approaches that are being exploited to manipulate the lesion environment affiliated with multiple neurodegenerative diseases and suggests that the utility of these approaches can extend to demyelination. Challenges are to further understand the roles of specific growth factors on a cellular and tissue level. Emerging technologies can then be employed to optimize the use of growth factors to ameliorate the deficits associated with demyelinating degenerative diseases.

Dysregulated fibroblast growth factor (FGF) signaling in neurological and psychiatric disorders

The role of the fibroblast growth factor (FGF) system in brain-related disorders has received considerable attention in recent years. To understand the role of this system in neurological and psychiatric disorders, it is important to identify the specific members of the FGF family that are implicated, their location and the various mechanisms they can be modulated. Each disorder appears to impact specific molecular players in unique anatomical locations, and all of these could conceivably become targets for treatment. In the last several years, the issue of how to target this system directly has become an area of increasing interest. To date, the most promising therapeutics are small molecule inhibitors and antibodies that modulate FGF receptor (FGFR) function. Beyond attempting to modify the primary players affected by a given brain disorder, it may prove useful to target molecules, such as membrane-bound or extracellular proteins that interact with FGF ligands or FGFRs to modulate signaling.

Fibroblast growth factors 1 and 2 in cerebrospinal fluid are associated with HIV disease, methamphetamine use, and neurocognitive functioning

Background

Human immunodeficiency virus (HIV) and methamphetamine use commonly affect neurocognitive (NC) functioning. We evaluated the relationships between NC functioning and two fibroblast growth factors (FGFs) in volunteers who differed in HIV serostatus and methamphetamine dependence (MAD).

Methods

A total of 100 volunteers were categorized into four groups based on HIV serostatus and MAD in the prior year. FGF-1 and FGF-2 were measured in cerebrospinal fluid by enzyme-linked immunosorbent assays along with two reference biomarkers (monocyte chemotactic protein [MCP]-1 and neopterin). Comprehensive NC testing was summarized by global and domain impairment ratings.

Results

Sixty-three volunteers were HIV+ and 59 had a history of MAD. FGF-1, FGF-2, and both reference biomarkers differed by HIV and MAD status. For example, FGF-1 levels were lower in subjects who had either HIV or MAD than in HIV− and MAD− controls (P=0.003). Multivariable regression identified that global NC impairment was associated with an interaction between FGF-1 and FGF-2 (model R²=0.09, P=0.01): higher FGF-2 levels were only associated with neurocognitive impairment among subjects who had lower FGF-1 levels. Including other covariates in the model (including antidepressant use) strengthened the model (model R²=0.18, P=0.004) but did not weaken the association with FGF-1 and FGF-2. Lower FGF-1 levels were associated with impairment in five of seven cognitive domains, more than FGF-2, MCP-1, or neopterin.

Conclusion

These findings provide in vivo support that HIV and MAD alter expression of FGFs, which may contribute to the NC abnormalities associated with these conditions. These cross-sectional findings cannot establish causality and the therapeutic benefits of recombinant FGF-1 need to be investigated.

Plasma biomarkers discriminate clinical forms of multiple sclerosis

Multiple sclerosis, the most common cause of neurological disability in young population after trauma, represents a significant public health burden. Current challenges associated with management of multiple sclerosis (MS) patients stem from the lack of biomarkers that might enable stratification of the different clinical forms of MS and thus prompt treatment for those patients with progressive MS, for whom there is currently no therapy available. In the present work we analyzed a set of thirty different plasma cytokines, chemokines and growth factors present in circulation of 129 MS patients with different clinical forms (relapsing remitting, secondary progressive and primary progressive MS) and 53 healthy controls, across two independent cohorts. The set of plasma analytes was quantified with Luminex xMAP technology and their predictive power regarding clinical outcome was evaluated both individually using ROC curves and in combination using logistic regression analysis. Our results from two independent cohorts of MS patients demonstrate that the divergent clinical and histology-based MS forms are associated with distinct profiles of circulating plasma protein biomarkers, with distinct signatures being composed of chemokines and growth/angiogenic factors. With this work, we propose that an evaluation of a set of 4 circulating biomarkers (HGF, Eotaxin/CCL11, EGF and MIP-1β/CCL4) in MS patients might serve as an effective tool in the diagnosis and more personalized therapeutic targeting of MS patients.

Fibroblast growth factor signalling in multiple sclerosis: inhibition of myelination and induction of pro-inflammatory environment by FGF9

Remyelination failure plays an important role in the pathophysiology of multiple sclerosis, but the underlying cellular and molecular mechanisms remain poorly understood. We now report actively demyelinating lesions in patients with multiple sclerosis are associated with increased glial expression of fibroblast growth factor 9 (FGF9), which we demonstrate inhibits myelination and remyelination in vitro. This inhibitory activity is associated with the appearance of multi-branched ‘pre-myelinating’ MBP⁺/PLP⁺ oligodendrocytes that interact with axons but fail to assemble myelin sheaths; an oligodendrocyte phenotype described previously in chronically demyelinated multiple sclerosis lesions. This inhibitory activity is not due to a direct effect of FGF9 on cells of the oligodendrocyte lineage but is mediated by factors secreted by astrocytes. Transcriptional profiling and functional validation studies demonstrate that these include effects dependent on increased expression of tissue inhibitor of metalloproteinase-sensitive proteases, enzymes more commonly associated with extracellular matrix remodelling. Further, we found that FGF9 induces expression of Ccl2 and Ccl7, two pro-inflammatory chemokines that contribute to recruitment of microglia and macrophages into multiple sclerosis lesions. These data indicate glial expression of FGF9 can initiate a complex astrocyte-dependent response that contributes to two distinct pathogenic pathways involved in the development of multiple sclerosis lesions. Namely, induction of a pro-inflammatory environment and failure of remyelination; a combination of effects predicted to exacerbate axonal injury and loss in patients.

Angiogenesis in multiple sclerosis and experimental autoimmune encephalomyelitis

Angiogenesis, the formation of new vessels, is found in Multiple Sclerosis (MS) demyelinating lesions following Vascular Endothelial Growth Factor (VEGF) release and the production of several other angiogenic molecules. The increased energy demand of inflammatory cuffs and damaged neural cells explains the strong angiogenic response in plaques and surrounding white matter. An angiogenic response has also been documented in an experimental model of MS, experimental allergic encephalomyelitis (EAE), where blood–brain barrier disruption and vascular remodelling appeared in a pre-symptomatic disease phase. In both MS and EAE, VEGF acts as a pro-inflammatory factor in the early phase but its reduced responsivity in the late phase can disrupt neuroregenerative attempts, since VEGF naturally enhances neuron resistance to injury and regulates neural progenitor proliferation, migration, differentiation and oligodendrocyte precursor cell (OPC) survival and migration to demyelinated lesions. Angiogenesis, neurogenesis and oligodendroglia maturation are closely intertwined in the neurovascular niches of the subventricular zone, one of the preferential locations of inflammatory lesions in MS, and in all the other temporary vascular niches where the mutual fostering of angiogenesis and OPC maturation occurs. Angiogenesis, induced either by CNS inflammation or by hypoxic stimuli related to neurovascular uncoupling, appears to be ineffective in chronic MS due to a counterbalancing effect of vasoconstrictive mechanisms determined by the reduced axonal activity, astrocyte dysfunction, microglia secretion of free radical species and mitochondrial abnormalities. Thus, angiogenesis, that supplies several trophic factors, should be promoted in therapeutic neuroregeneration efforts to combat the progressive, degenerative phase of MS.

Fibroblast growth factor-2 signaling in neurogenesis and neurodegeneration

Fibroblast growth factor-2 (FGF2), also known as basic FGF, is a multi-functional growth factor. One of the 22-member FGF family, it signals through receptor tyrosine kinases encoding FGFR1-4. FGF2 activates FGFRs in cooperation with heparin or heparin sulfate proteoglycan to induce its pleiotropic effects in different tissues and organs, which include potent angiogenic effects and important roles in the differentiation and function of the central nervous system (CNS). FGF2 is crucial to development of the CNS, which explains its importance in adult neurogenesis. During development, high levels of FGF2 are detected from neurulation onwards. Moreover, developmental expression of FGF2 and its receptors is temporally and spatially regulated, concurring with development of specific brain regions including the hippocampus and substantia nigra pars compacta. In adult neurogenesis, FGF2 has been implicated based on its expression and regulation of neural stem and progenitor cells in the neurogenic niches, the subventricular zone (SVZ) and the subgranular zone (SGZ) of the hippocampal dentate gyrus. FGFR1 signaling also modulates inflammatory signaling through the surface glycoprotein CD200, which regulates microglial activation. Because of its importance in adult neurogenesis and neuroinflammation, manipulation of FGF2/FGFR1 signaling has been a focus of therapeutic development for neurodegenerative disorders, such as Alzheimer's disease, multiple sclerosis, Parkinson's disease and traumatic brain injury. Novel strategies include intranasal administration of FGF2, administration of an NCAM-derived FGFR1 agonist, and chitosan-based nanoparticles for the delivery of FGF2 in pre-clinical animal models. In this review, we highlight current research towards therapeutic interventions targeting FGF2/FGFR1 in neurodegenerative disorders.

Intrathecal oligoclonal IgG synthesis in multiple sclerosis

The diagnosis of multiple sclerosis is based on dissemination in time and space. Before 2010 lack of evidence for dissemination in space could be substituted by a paraclinical test, cerebrospinal fluid (CSF) oligoclonal bands (OCBs). The present meta-analysis (13,467 patients) shows that the diagnostic specificity of OCB drops from 94% to 61% if inflammatory etiologies are considered. Importantly, this was not caused by poor laboratory practice. This review on CSF OCB further illustrates the conceptional problem of substituting dissemination in space with a biomarker. The potential prognostic value of intrathecal OCB will need to be tested prospectively.

RANTES and fibroblast growth factor 2 in jawbone cavitations: triggers for systemic disease?

Background

Jawbone cavitations (JC) are hollow dead spaces in jawbones with dying or dead bone marrow. These areas are defined as fatty degenerative osteonecrosis of the jawbone or neuralgia-inducing cavitational osteonecrosis and may produce facial pain. These afflictions have been linked to the immune system and chronic illnesses. Surgical debridement of JC is reported to lead to an improvement in immunological complaints, such as rheumatic, allergic, and other inflammatory diseases (ID). Little is known about the underlying cause/effect relationship.

Objectives

JC bone samples were analyzed to assess the expression and quantification of immune modulators that can play a role in the pathogenesis of IDs. The study supports a potential mechanism where JC is a mediating link in IDs.

Materials and methods

Samples of fatty softened bone taken from JCs were extracted from 31 patients. The specimens were analyzed by bead-based multiplex technology and tested for seven immune messengers.

Results

Regulated upon activation, normal T-cell expressed, and secreted (RANTES) and fibroblast growth factor (FGF)-2 were found at high levels in the JCs tested. Other cytokines could not be detected at excessive levels.

Discussion

The study confirms that JC is able to produce inflammatory messengers, primarily RANTES, and, secondarily, FGF-2. Both are implicated in many serious illnesses. The excessive levels of RANTES/FGF-2 in JC patients with amyotrophic lateral sclerosis, multiple sclerosis, rheumatoid arthritis, and breast cancer are compared to levels published in medical journals. Levels detected in JCs are higher than in the serum and cerebrospinal fluid of amyotrophic lateral sclerosis and multiple sclerosis patients and four-fold higher than in breast cancer tissue.

Conclusion

This study suggests that JC might serve as a fundamental cause of IDs, through RANTES/FGF-2 production. Thus, JC and implicated immune messengers represent an integrative aspect of IDs and serve as a possible cause. Removing JCs may be a key to reversing IDs. There is a need to raise awareness about JC throughout medicine and dentistry.

Expression and Genetic Analysis of MicroRNAs Involved in Multiple Sclerosis

Evidence underlines the importance of microRNAs (miRNAs) in the pathogenesis of multiple sclerosis (MS). Based on the fact that miRNAs are present in human biological fluids, we previously showed that miR-223, miR-23a and miR-15b levels were downregulated in the sera of MS patients versus controls. Here, the expression levels of these candidate miRNAs were determined in peripheral blood mononuclear cells (PBMCs) and the serum of MS patients, in addition to three genotyped single nucleotide polymorphisms (SNPs). Mapping in the genomic regions of miR-223, miR-23a and miR-15b genes, 399 cases and 420 controls were tested. Expression levels of miR-223 and miR-23a were altered in PBMCs from MS patients versus controls. Conversely, there were no differences in the expression levels of miR-15b. A significantly decreased genotypic frequency of miR-223 rs1044165 T/T genotype was observed in MS patients. Moreover, the allelic frequency of miR-23a rs3745453 C allele was significantly increased in patients versus controls. In contrast, there were no differences in the distribution of miR-15b SNP. In conclusion, our results suggest that miR-223 and miR-23a could play a role in the pathogenesis of MS. Moreover, miR-223 rs1044165 polymorphism likely acts as a protective factor, while miR-23a rs3745453 variant seems to act as a risk factor for MS.

Signalling pathways that inhibit the capacity of precursor cells for myelin repair

In demyelinating disorders such as Multiple Sclerosis (MS), targets of injury are myelin and oligodendrocytes, leading to severe neurological dysfunction. Regenerative therapies aimed at promoting oligodendrocyte maturation and remyelination are promising strategies for treatment in demyelinating disorders. Endogenous precursor cells or exogenous transplanted cells are potential sources for remyelinating oligodendrocytes in the central nervous system (CNS). Several signalling pathways have been implicated in regulating the capacity of these cell populations for myelin repair. Here, we review neural precursor cells and oligodendrocyte progenitor cells as potential sources for remyelinating oligodendrocytes and evidence for the functional role of key signalling pathways in inhibiting regeneration from these precursor cell populations.

MicroRNAs as active players in the pathogenesis of multiple sclerosis

MicroRNAs (miRNAs) are a recently discovered group of small noncoding RNAs that regulate gene expression post-transcriptionally. They are highly expressed in cells of the immune system, as well as in the central nervous system, and they are deregulated in various neurological disorders. Emerging evidence underlines an involvement of miRNAs in the pathogenesis of Multiple Sclerosis (MS). A number of miRNAs have been found to be dysregulated in blood cells from MS patients, in brain lesions, as well as in biological fluids such as serum and plasma. Despite miRNA altered expression likely showing a high tissue specificity, some profile similarities could be observed for certain miRNAs such as miR-326-such as upregulation in both active lesions and blood-though not for others such as miR-323, which demonstrated upregulation in whole blood, active brain lesions, and T-reg cells, but not in the serum of MS patients. In this review, the possible role of miRNAs in MS pathogenesis will be discussed according to all the available literature, with a particular emphasis on the possibility of considering extracellular miRNAs as a new source for both biomarker identification and therapeutic target discovery.

Neuroprotective and memory enhancing properties of a dual agonist of the FGF receptor and NCAM

The fibroblast growth factor receptor (FGFR) plays a vital role in the development of the nervous system regulating a multitude of cellular processes. One of the interaction partners of the FGFR is the neural cell adhesion molecule (NCAM), which is known to play an important role in neuronal development, regeneration and synaptic plasticity. Thus, simultaneous activation of FGFR- and NCAM-mediated signaling pathways may be expected to affect processes underlying neurodegenerative diseases. We here report the identification of a peptide compound, Enreptin, capable of interacting with both FGFR and NCAM. We demonstrate that this dual specificity agonist induces phosphorylation of FGFR and differentiation and survival of primary neurons in vitro, and that these effects are inhibited by abrogation of both NCAM and FGFR signaling pathways. Furthermore, Enreptin crosses the blood-brain barrier after subcutaneous administration, enhances long-term memory in normal mice and ameliorates memory deficit in mice with induced brain inflammation. Moreover, Enreptin reduces cognitive impairment and neuronal death induced by Aβ25-35 in a rat model of Alzheimer's disease, and reduces the mortality rate and clinical signs of experimental autoimmune encephalomyelitis in rats. Thus, Enreptin is an attractive candidate for the treatment of neurological diseases.

FGF-2 and Anosmin-1 are selectively expressed in different types of multiple sclerosis lesions

Multiple sclerosis is a demyelinating disease that affects ≈ 2,000,000 people worldwide. In the advanced stages of the disease, endogenous oligodendrocyte precursors cannot colonize the lesions or differentiate into myelinating oligodendrocytes. During development, both FGF-2 and Anosmin-1 participate in oligodendrocyte precursor cell migration, acting via the FGF receptor 1 (FGFR1). Hence, we performed a histopathological and molecular analysis of these developmental modulators in postmortem tissue blocks from multiple sclerosis patients. Accordingly, we demonstrate that the distribution of FGF-2 and Anosmin-1 varies between the different types of multiple sclerosis lesions: FGF-2 is expressed only within active lesions and in the periplaque of chronic lesions, whereas Anosmin-1 is upregulated within chronic lesions and is totally absent in active lesions. We show that the endogenous oligodendrocyte precursor cells recruited toward chronic-active lesions express FGFR1, possibly in response to the FGF-2 produced by microglial cells in the periplaque. Also in human tissue, FGF-2 is upregulated in perivascular astrocytes in regions of the normal-appearing gray matter, where the integrity of the blood-brain barrier is compromised. In culture, FGF-2 and Anosmin-1 influence adult mouse oligodendrocyte precursor cell migration in the same manner as at embryonic stages, providing an explanation for the histopathological observations: FGF-2 attracts/enhances its migration, which is hindered by Anosmin-1. We propose that FGF-2 and Anosmin-1 are markers for the histopathological type and the level of inflammation of multiple sclerosis lesions, and that they may serve as novel pharmacogenetic targets to design future therapies that favor effective remyelination and protect the blood-brain barrier.

How factors secreted from astrocytes impact myelin repair

Over a century ago, hypertrophy of astrocytes was noted as a pathology of multiple sclerosis (MS) and was hypothesized to play an important role in this disease, yet the contribution of astrocytes has been largely underemphasized in the pathophysiology of CNS demyelination. Astrocytes perform many homeostatic functions within the developing and adult CNS, including enhancing formation and maintenance of the blood-brain barrier, moderating neuronal connections through the tripartite synapse, and perhaps even offering intercellular communication independently of neurons. Although there is a significant body of literature characterizing different types of MS lesions, the inflammatory demyelination in an active MS lesion is accompanied by the presence of macrophages, lymphocytes, and large reactive astrocytes. The astrocyte has long been viewed as a cell that promotes inflammation and demyelination, while also forming the glial scar, thus hindering remyelination and axon growth. Renewed interest in the astrocyte has been brought about by recent studies demonstrating that astrocytes can also function as cellular mediators of CNS myelination by promoting oligodendrocyte progenitor migration, proliferation, and differentiation. Thus, refining our knowledge of astrocytic functions in the regulation of CNS myelination may help us to better understand why remyelination fails in MS.

Neuroprotective role of fibroblast growth factor-2 in experimental autoimmune encephalomyelitis

The role of fibroblast growth factor-2 (FGF-2) in multiple sclerosis and its animal model experimental autoimmune encephalomyelitis is discussed. This study is the first to use FGF-2(-/-) mice to further address the involvement of FGF-2 in the disease process. We demonstrate that immunization with myelin oligodendrocyte glycoprotein peptide 35-55 induces more severe experimental autoimmune encephalomyelitis in FGF-2(-/-) mice compared with FGF-2(+/+) mice. The antigen-specific cytokine response to myelin oligodendrocyte glycoprotein peptide and the degree of central nervous system inflammation was similar in both groups. However, FGF-2(-/-) mice displayed increased infiltration of CD8(+) T cells and macrophages/microglia. In addition, nerve fibre degeneration and axonal loss were augmented, whereas the extent of remyelination in central nervous system lesions was reduced. FGF-2 has been associated with the induction of demyelination and the inhibition of myelin production by oligodendrocytes. Our study supports the opposing notion that FGF-2 can also assert a neuroprotective function. This may be particularly appealing when it comes to targeting the neurodegenerative aspect of multiple sclerosis.

Neurodegeneration in a transgenic mouse model of multiple system atrophy is associated with altered expression of oligodendroglial-derived neurotrophic factors

Multiple system atrophy (MSA) is a neurodegenerative disorder characterized by striatonigral degeneration and olivo-pontocerebellar atrophy. Neuronal degeneration is accompanied by primarily oligodendrocytic accumulation of alpha-synuclein (alphasyn) as opposed to the neuronal inclusions more commonly found in other alpha-synucleinopathies such as Parkinson's disease. It is unclear how alphasyn accumulation in oligodendrocytes may lead to the extensive neurodegeneration observed in MSA; we hypothesize that the altered expression of oligodendrocyte-derived neurotrophic factors by alphasyn may be involved. In this context, the expression of a number neurotrophic factors reportedly expressed by oligodendrocytes [glial-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), and insulin-like growth factor 1 (IGF-1), as well as basic fibroblast growth factor 2 (bFGF2), reportedly astrocyte derived] were examined in transgenic mouse models expressing human alphasyn (halphasyn) under the control of either neuronal (PDGFbeta or mThy1) or oligodendrocytic (MBP) promoters. Although protein levels of BDNF and IGF-1 were altered in all the alphasyn transgenic mice regardless of promoter type, a specific decrease in GDNF protein expression was observed in the MBP-halphasyn transgenic mice. Intracerebroventricular infusion of GDNF improved behavioral deficits and ameliorated neurodegenerative pathology in the MBP-halphasyn transgenic mice. Consistent with the studies in the MBP-halphasyn transgenic mice, analysis of GDNF expression levels in human MSA samples demonstrated a decrease in the white frontal cortex and to a lesser degree in the cerebellum compared with controls. These results suggest a mechanism in which alphasyn expression in oligodendrocytes impacts on the trophic support provided by these cells for neurons, perhaps contributing to neurodegeneration.